<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- 不要让用户提交包含 "form" 和 "formaction"属性的标签.避免在form中出现id属性及提交按钮.  -->
    <form id="test"></form>
    <button form="test" formaction="javascript:alert(1)">X</button>
  </body>
</html>
